23. Fossil Gaps

If evolution happened, the fossil record should show continuous and gradual changes from the bottom to the top layers. Actually, many gaps or discontinuities appear throughout the fossil record.a At the most fundamental level, a big gap exists between forms of life whose cells have nuclei (eukaryotes, such as plants, animals, and fungi) and those that don’t (prokaryotes, such as bacteria and blue-green algae).b Fossil links are also missing between large groupings of plants,c between single-celled forms of life and invertebrates (animals without backbones), among insects,d between invertebrates and vertebrates (animals with backbones),e between fish and amphibians,f between amphibians and reptiles,g between reptiles and mammals,h between reptiles and birds,i between primates and other mammals,j and between apes and other primates.k In fact, chains are missing, not links. The fossil record has been studied so thoroughly that it is safe to conclude that these gaps are real; they will never be filled.l